The invention concerns an anchoring element with a screw comprising a threaded section and a head designed as a spherical segment-shaped section, and with a receiving portion for connecting the screw to a rod. An anchoring element of this kind is used in particular in vertebral column surgery, but also in accident surgery on other bones.
Such an anchoring element is known from DE 43 07 576 C1, for example. With known anchoring elements and screws of this kind, the threaded section of the screw and its head are constructed in one piece. As the surgeon needs very different lengths of screws, he must always have different sets of such screws available. This makes a considerable stockpile necessary, resulting in considerable costs.
It is the object of the invention to eliminate this drawback.
This object is achieved by an anchoring element with a screw (12) comprising a threaded section (13) and a head (15) designed as a spherical segment-shaped section, and with a receiving portion (1) for connecting the screw (12) to a rod (19), wherein the receiving portion (1) comprises a first end (2) and a second end (3) opposite the latter, a longitudinal axis (4) passing through the two ends (2, 3), a bore (5) coaxial with the longitudinal axis (4), a firs t region adjoining the first end (2) with an essentially Us shaped cross-section (7) with two free arms (8, 9) comprising a thread for receiving the rod (19) to be inserted, a region adjoining the other end (3) for receiving the head (15), and an element (22, 17) which exerts pressure on the rod (19) or on the head (15), characterised in that the threaded section (13) and the head (15) are designed as separate parts.
As a r result it is possible for the surgeon during application to shorten the threaded section to a desired length before or after implanting, and then connect it to the head and the receiving portion. In this way the maintenance of stocks is substantially reduced, and at the same time the possibilities for the Burgeon to make finer adjustments are increased, as the screws can be shortened to any length.
Further embodiments of the invention include one or more of the following features:
the threaded section (13) comprises a shank (14) at the head end;
the head (15) comprises a spring-yielding edge on its side facing towards the threaded section (13);
the edge (34) facing towards the threaded section comprises one or more apertures or recesses (28, 29, 33) which are directed parallel to the axis of symmetry (4) and distributed circumferentially;
an aperture (33) extends over the whole wall length, seen in a direction parallel to the axis of symmetry (4);
the head (15) comprises a bore (27) coaxial with the axis of symmetry;
the bore (27) is cylindrical;
the shank (14) comprises a rough surface;
the shank (14) is polygonal;
the head (15) comprises an internal thread in the bore and the shank (35) comprises an external thread mating therewith; and/or
the head (15) is corrugated in the circumferential direction in the bore and the shank (37) comprises a corresponding corrugation on its outer side.
Further characteristics and suitabilities of the invention are apparent from the description of practical examples with the aid of the figures.